This invention relates to an acceleration detector for detecting the acceleration of a moving body such as an automobile.
Among the known acceleration detectors, there is one in which the motion of a magnetic body moving under acceleration is detected by use of a differential transformer.
FIG. 5 shows one example. If acceleration is applied to this acceleration detector 41 in the direction A in this figure, a magnetic body 44 supported by leaf springs 43a and 43b moves in the direction B while resiliently deforming the leaf springs. By this movement, the portion of the magnetic body 44 that is present inside a righthand secondary coil 47b will be longer than its portion located inside a lefthand secondary coil 47a. This produces a difference in induced voltage between the secondary coils 47a and 47b. The acceleration is detected by this difference.
In FIG. 5, reference numeral 46 designates a primary coil and 42 a case. One example of this type of detector is disclosed in Japanese Utility Model Unexamined Publication No. 59-95266.
With this type of detector, since an induced voltage difference is produced between the right and left secondary coils in response to the relative displacement between the secondary coils and the magnetic body, the magnetic reluctance between the primary coil and the secondary coils is rather large and thus the sensitivity of detection tends to be low. Further, in order to stabilize its performance, the parts have to be positioned relative to each other with high accuracy. This requires time-consuming adjustment work and thus the efficiency of assembly is low and the assembling cost high. Moreover, since there is no standard for positioning, accurate adjustment is difficult, which will makes it difficult to achieve performance stability.